High-performance lignocellulosic composites with whole-component utilization

As one of the most promising alternatives to petroleum-based polymers, biomass presents a heterogeneous structure constructed via complex association interactions among the natural organic macromolecules such as cellulose, lignin and hemicellulose, which cannot be directly molded by conventional processing technologies. Component separation has long been adopted to extract the linear-structured cellulose, known as biorefining in academia and pulping in industry. The isolated cellulose is further processed via dissolution–regeneration routes to fabricate regenerated fibers, films and related products. Nevertheless, this approach greatly depreciates the utilization value of lignin and hemicellulose, and even leads to their abandonment and subsequent environmental pollution. Recent advances reveal that the lignocellulosic biomass can be directly transformed into lignocellulosic materials by appropriate strategies without tedious component separation. In this review, we highlight the latest progress in the direct fabrication of high-strength, tough and lightweight composites from renewable lignocellulosic biomass under the philosophy of whole-component utilization. The chemical components and multilayered structures of the typical lignocellulosic biomass are systematically summarized. To realize the whole-component biomass, two dominant strategies, namely pressure-induced densification and whole-component regeneration, are introduced. The research progress of the two strategies as well as their effects on the structural evolution and performance regulation of lignocellulosic composites are discussed. Furthermore, the inherent structural advantages enable lignocellulosic composites to serve as promising candidates for the design of advanced functional materials, with broad applications in thermal management, electromagnetic interference shielding and water resistance.